Method and apparatus for compression molding plastic articles

Abstract

A method and apparatus for compression molding plastic articles such as closures include a plurality of tools mounted in opposed pairs with the tools of each pair including opposed male and female mold sections. The tool pairs are mounted for motion in an endless path. The tool pairs and associated mold sections are closed during motion in the path for compression a molding charge in the mold cavity formed between the mold sections of each pair, and opening the mold cavity to release an article formed between the mold sections. A latch mechanism is associated with each pair of tools for holding the tools and mold sections in the closed position during motion in the path independent of the mechanism for closing the tools and mold halves. In this way, forces imparted to the mold halves and tools to hold the mold closed are isolated from the machine frame. The latch mechanism is selectively unlatched to permit opening of the mold halves and release of the article compression-molded between the mold halves.

What is claimed is:  
     
       1. Apparatus for compression molding plastic articles which includes: 
       a plurality of female mold tools mounted for motion about an axis in an endless path, each of said female mold tools including at least two female mold cavities that are radially spaced from each other with respect to said axis,  
       a mold charge delivery system positioned above said female mold tools in a portion of said endless path, said mold charge delivery system including inlet means for receiving extruded plastic and at least two outlets for delivering plastic mold charges to the at least two female mold cavities of each female mold tool in turn as each female mold tool passes beneath said mold charge delivery system, and  
       a plurality of male mold tools, each including at least two male mold elements for movement against said female mold tools to compression mold plastic mold charges in said female mold cavities during at least a portion of motion of said female mold tools in said endless path,  
       said mold charge delivery system including means for severing mold charges of plastic extrudate at said outlets and delivering severed plastic mold charges to said at least two female mold cavities, and means for rotating said severing means about a second axis in synchronism with motion of said female mold tools in said endless path.  
     
     
       2. The apparatus set forth in  claim 1  wherein said at least two female mold cavities are radially aligned with said axis. 
     
     
       3. The apparatus set forth in  claim 1  wherein said mold charge delivery system delivers said plastic mold charges simultaneously to all mold cavities of each said female mold tool in sequence. 
     
     
       4. The apparatus set forth in  claim 1  wherein said mold charge delivery system further includes means for delivering air under pressure to said severing means to promote separation of said plastic mold charges from said severing means when said severing means overlie said female mold cavities. 
     
     
       5. The apparatus set forth in  claim 1  wherein said female mold cavities are disposed in concentric arrays in said female mold tools. 
     
     
       6. The apparatus set forth in  claim 5  wherein said mold charge delivery system includes: 
       a disk disposed to rotate about a second axis so as to rotate a periphery of said disk overlying said female mold tools,  
       first and second circumferentially spaced arrays of mold charge transfer means on said disk periphery spaced radially from each other with respect to said second axis by a distance so as to bring said transfer means into overlying position with respect to said concentric arrays of mold cavities, and  
       means for rotating said disk in synchronism with travel of said female mold tools in said endless path.  
     
     
       7. The apparatus set forth in  claim 6  wherein said disk periphery includes a first portion in which an inner of said transfer means arrays is disposed, and a second portion in which an outer of said transfer means arrays is disposed, said second portion being circumferentially adjustable with respect to said first portion for timing transfer of mold charges to said concentric arrays. 
     
     
       8. Apparatus for compression molding plastic articles which includes: 
       a plurality of female mold tools mounted for motion about an axis in an endless path, each of said female mold tools including at least two female mold cavities that are radially spaced from each other with respect to said axis,  
       a mold charge delivery system positioned above said female mold tools in a portion of said endless path, said mold charge delivery system including inlet means for receiving extruded plastic and at least two outlets for delivering plastic mold charges to the at least two female mold cavities of each female mold tool in turn as each female mold tool passes beneath said mold charge delivery system, and  
       a plurality of male mold tools, each including at least two male mold elements for movement against said female mold tools to compression mold plastic mold charges in said female mold cavities during at least a portion of motion of said female mold tools in said endless path,  
       said mold charge delivery system including means for severing mold charges of plastic extrudate at said outlets and delivering severed plastic mold charges to said at least two female mold cavities, and means for delivering air under pressure to said severing means to promote separation of said plastic mold charges from said severing means when said severing means overlie said female mold cavities.  
     
     
       9. The apparatus set forth in  claim 8  wherein said mold charge delivery system further includes means for rotating said severing means about a second axis in synchronism with motion of said female mold tools in said endless path. 
     
     
       10. The apparatus set forth in  claim 8  wherein said at least two female mold cavities are radially aligned with said axis. 
     
     
       11. The apparatus set forth in  claim 8  wherein said mold charge delivery system delivers said plastic mold charges simultaneously to all mold cavities of each said female mold tool in sequence. 
     
     
       12. The apparatus set forth in  claim 8  wherein said female mold cavities are disposed in concentric arrays in said female mold tools. 
     
     
       13. The apparatus set forth in  claim 12  wherein said mold charge delivery system includes: 
       a disk disposed to rotate about a second axis so as to rotate a periphery of said disk overlying said female mold tools,  
       first and second circumferentially spaced arrays of mold charge transfer means on said disk periphery spaced radially from each other with respect to said second axis by a distance so as to bring said transfer means into overlying position with respect to said concentric arrays of mold cavities, and  
       means for rotating said disk in synchronism with travel of said female mold tools in said endless path.  
     
     
       14. The apparatus set forth in  claim 13  wherein said disk periphery includes a first portion in which an inner of said transfer means arrays is disposed, and a second portion in which an outer of said transfer means arrays is disposed, said second portion being circumferentially adjustable with respect to said first portion for timing transfer of mold charges to said concentric arrays. 
     
     
       15. Apparatus for compression molding plastic articles which includes: 
       a plurality of female mold tools mounted for motion about an axis in an endless path, each of said female mold tools including at least two female mold cavities that are radially spaced from each other with respect to said axis, said female mold cavities being disposed in concentric arrays in said female mold tools,  
       a mold charge delivery system positioned above said female mold tools in a portion of said endless path, said mold charge delivery system including inlet means for receiving extruded plastic and at least two outlets for delivering plastic mold charges to the at least two female mold cavities of each female mold tool in turn as each female mold tool passes beneath said mold charge delivery system, and  
       a plurality of male mold tools, each including at least two male mold elements for movement against said female mold tools to compression mold plastic mold charges in said female mold cavities during at least a portion of motion of said female mold tools in said endless path,  
       said mold charge delivery system including:  
       a disk disposed to rotate about a second axis so as to rotate a periphery of said disk overlying said female mold tools,  
       first and second circumferentially spaced arrays of mold charge transfer means on said disk periphery spaced radially from each other with respect to said second axis by a distance so as to bring said transfer means into overlying position with respect to said concentric arrays of mold cavities, and  
       means for rotating said disk in synchronism with travel of said female mold tools in said endless path.  
     
     
       16. The apparatus set forth in  claim 15  wherein said mold charge delivery system includes means for severing charges of plastic extrudate at said outlets and delivering severed plastic mold charges to said at least two female mold cavities. 
     
     
       17. Apparatus for compression molding plastic articles which includes: 
       a plurality of female mold tools mounted for motion about an axis in an endless path, each of said female mold tools including at least two female mold cavities that are radially spaced from each other with respect to said axis,  
       a mold charge delivery system positioned above said female mold tools in a portion of said endless path, said mold charge delivery system including means for severing mold charges of plastic and delivering severed plastic mold charges substantially simultaneously to the at least two female mold cavities of each female mold tool in turn as each female mold tool passes beneath said mold charge delivery system, and  
       a plurality of male mold tools, each including at least two male mold elements for movement against said female mold tools to compression mold plastic mold charges in said female mold cavities during at least a portion of motion of said female mold tools in said endless path,  
       said mold charge delivery system further including means for rotating said severing means about a second axis in synchronism with motion of said female mold tools in said endless path.  
     
     
       18. The apparatus set forth in  claim 17  wherein said mold charge delivery system further includes means for delivering air under pressure to said severing means to promote separation of said plastic mold charges from said severing means where said severing means overlie said female mold cavities. 
     
     
       19. Apparatus for compression molding plastic articles which includes: 
       a plurality of female mold tools mounted for motion about an axis in an endless path, each of said female mold tools including at least two female mold cavities that are radially spaced from each other with respect to said axis,  
       a mold charge delivery system positioned above said female mold tools in a portion of said endless path, said mold charge delivery system including means for severing mold charges of plastic and delivering severed plastic mold charges substantially simultaneously to the at least two female mold cavities of each female mold tool in turn as each female mold tool passes beneath said mold charge delivery system, and  
       a plurality of male mold tools, each including at least two male mold elements for movement against said female mold tools to compression mold plastic mold charges in said female mold cavities during at least a portion of motion of said female mold tools in said endless path,  
       said mold charge delivery system further including means for delivering air under pressure to said severing means to promote separation of said plastic mold charges from said severing means where said severing means overlie said female mold cavities.  
     
     
       20. The apparatus set forth in  claim 19  wherein said mold charge delivery system further includes means for rotating said severing means about a second axis in synchronism with motion of said female mold tools in said endless path.